The present invention relates to a switching device for multiple (dual) focus points of multiple (dual) optical paths, and especially to a switching device in which various scanning optical paths or dual optical paths can be performed.
As show in FIG. 1, the current scanning optical path device includes a glass 1 arranged in a scanner (not shown) and for supporting a document, a reflector 2 below the glass 1, a primary lens 3 with respect to the reflector 2 and arranged at one side in the scanner, a sensing element 4 behind the primary lens 3. After the document is radiated by light, the image of the scanning article is reflected by the reflector 2, then is projected to a lens 3, and then is received by the sensing element 4 so as to read the image of the document. In order to prevent that the transmitted original document, such as a positive piece or a negative piece, placed above the glass 1, a frame is added. By the width of the frame, the original document is placed higher than the surface of the glass with a distance so as to generate Newton rings (interference strips) in scanning so that the scanning effect is not preferred.
In the feeding process of an auto paper feeding, the original document is effected by a guide piece of the auto paper feeder so that the original document can not be correctly in the focus plane (that in the surface of the glass in the scanner). Therefore, Newton ring (interference strips) occurs so as to induce a bad image.
In order to solve the aforesaid problem, in another scanning optical path device (such as that shown in FIGS. 2A and 2B), a lenses with thickness t is arranged between a reflector 2 and a primary lens 3 (according to principle of optics, a lenses with reflectivity of 1.5, the optical path is increased to 1/3 of the thickness, namely, the original document is placed above the surface with a length of t/3). When the lenses t is switched to be between the reflector 2 and the primary lens 3, the second focus point d' has a height h being approximate equal to t/3. Thus, the original document is placed above the original focus point d.
However, this design has solved some prior art problems, but the optical path and focus points are fixed so not to be changed and thus, it can not be suitable in various conditions for acquiring a clear image. Therefore, there is an eager demand for a novel switching device for multiple (dual) focus points of multiple (dual) optical paths for improving the defects in the prior art designs.